1. Field of the Invention
The present invention relates to a shift-brake device of a twin-shaft hinge, and in particular relates to a shift-brake device with small volume, simple operation and ideal lock-in effect in sequence rotation.
2. Description of the Related Art
Referring to FIGS. 1 and 2, a conventional double rotary shaft hinge device mainly includes a first pivot shaft 30, a second pivot shaft 40, a packing assembly 6, a pivotal positioning assembly 7 and a pivotal limit sheet 8. The first and second pivot shafts 30 and 40 include positioning planes 301 and 401, connecting portions 302 and 402, and fixing portions 303 and 403. In the first and second pivot shafts 30 and 40, the positioning planes 301 and 401 are respectively configured on regions extending from middle sections toward first end portions, the fixing portions 303 and 403 (e.g., external screw threads) are respectively configured on first end portions thereof, and the connecting portions 302 and 402 are respectively configured on second end portions thereof to couple with a pivotal member (e.g., a liquid crystal monitor) and a relative pivotal member (e.g., a host body).
The packing assembly 6 includes elastic portions 61 and 62, a positioning portion 63 (e.g., a threaded hole) and a base body 65. In the packing assembly 6, the base body 65 can be implemented by cooperating with a separate spacer positioning sheet 2a, and the base body 65 and the spacer positioning sheet 2a are respectively correspondingly configured with through holes 651/652 and 21a/22a which are provided for being penetrated through by the first and second pivot shafts 30 and 40. The spacer positioning sheet 2a is configured with an elongated slot 23a located between the two through holes 21a and 22a. One side of the base body 65, which is apart from the spacer positioning sheet 2a relative to the through holes 651 and 652, is respectively connected with the elastic portions 61 and 62. The elastic portions 61 and 62 of the packing assembly 6 are sleeved on one end portions of the first and second pivot shafts 30 and 40 which are provided with the positioning planes 301 and 401. Two fixing members 304 and 404 (e.g., screw nuts) are utilized to respectively engage with the fixing portions 303 and 403 (the external screw threads) of the first and second pivot shafts 30 and 40, so that a packing condition with elasticity can be kept between the first and second pivot shafts 30 and 40 and the base body 65 of the packing assembly 6, i.e., the first and second pivot shafts 30 and 40 can be prevented from being released from the packing assembly 6 respectively. The positioning portion 63 (the threaded hole) configured on the base body 65 is located between the elastic portions 61 and 62.
The pivotal limit sheet 8, which is configured on one side of the base body 65 of the packing assembly 6 apart from the elastic portions 61 and 62 thereof, includes two through holes 81 and 82 which are corresponding to the through holes 651 and 652 of the base body 65, two stop portions 811 and 821 which are configured on sides of external peripheries of the through holes 81 and 82 with different limit ranges of dimensions and angles, and an elongated slot 83 located between the two through holes 81 and 82.
The pivotal positioning assembly 7, which is configured between the pivotal limit sheet 8 and the spacer positioning sheet 2a, includes two linking wheels 71 and 72 and a movable wheel 73. The linking wheels 71 and 72 respectively include coupling holes 711 and 721, positioning concave portions 712 and 722 and side convex portions 713 and 723, in which the coupling holes 711 and 721 are respectively configured on centers thereof and capable of being sleeved on the positioning planes 301 and 401 of the first and second pivot shafts 30 and 40, the positioning concave portions 712 and 722 are respectively configured on external peripheries thereof, and the side convex portions 713 and 723 are respectively configured on lateral sides thereof. The side convex portions 713 and 723 of the linking wheels 71 and 72 are respectively limited by the stop portions 811 and 821 of the pivotal limit sheet 8, thus to form different pivotal limit ranges of dimensions and angles. The movable wheel 73 includes a support shaft 731 which is configured on a center thereof and with convex extensions. With two end portions of the support shaft 731 of the movable wheel 73 to respectively enter into the elongated slot 23a of the spacer positioning sheet 2a and the elongated slot 83 of the pivotal limit sheet 8, the movable wheel 73 is allowed to slide within a limit region. An elastic sheet 74 disposed between the movable wheel 73 and the pivotal limit sheet 8 includes a central hole 741, in which the central hole 741 is configured on a center thereof and capable of being sleeved on the support shaft 731 of the movable wheel 73. With the elastic sheet 74, the movable wheel 73 can be kept in packing contact condition together with the linking wheels 71 and 72.
In one example, the above-described assembles and components of the conventional double rotary shaft hinge device can be disposed in a predetermined containing space 501 of an external sleeve tube 50. The external sleeve tube 50 includes the containing space 501 and a to-be-positioned portion 503 (e.g., a through hole), in which one side of the containing space 501 is closed, and the to-be-positioned portion 503 is corresponding to the positioning portion 63 (the threaded hole) of the packing assembly 6. A positioning element 631 (e.g., a bolt) is utilized to pass through the to-be-positioned portion 503 of the external sleeve tube 50 to screw into the positioning portion 63 of the packing assembly 6, so that the locking assembly I and the packing assembly 6 can be connectively positioned with the external sleeve tube 50.
Referring to FIGS. 3, 4, 5, 6 and 7, in practical use of the conventional double rotary shaft hinge device, when the pivotal member (the liquid crystal monitor) and the relative pivotal member (the host body) are situated in a relatively covered storage condition, the first and second pivot shafts 30 and 40 are respectively utilized to link the linking wheels 71 and 72 of the pivotal positioning assembly 7 to face the positioning concave portions 712 and 722 toward the same side (as shown in FIG. 3). As shown in the figures, one side portion of the linking wheel 71 apart from the positioning concave portion 712 is pushed against the movable wheel 73 to embed into the positioning concave portion 722 of the linking wheel 72. Meanwhile, the first pivot shaft 30 is allowed to continuously rotate due to mutually propping contact between relative convex arc surfaces of the linking wheel 71 and the movable wheel 73, and the second pivot shaft 40 is situated in a fixed unpivoted condition (as shown in FIG. 4) in the pivoting process. Then, the positioning concave portion 712 of the linking wheel 71 is rotated to face toward the movable wheel 73 (as shown in FIG. 5) to release the propping contact to the movable wheel 73 until the first pivot shaft 30 drives the linking wheel 71 to pivot with a predetermined angle (about 180 degrees in the figures). At this time, the movable wheel 73 is allowed to slide in an extension direction of the elongated slot 23a of the spacer positioning sheet 2a and the elongated slot 83 of the pivotal limit sheet 8, and the second pivot shaft 40 (the linking wheel 72 of the pivotal positioning assembly 7) is situated in a pivotable condition.
Then, as shown in FIG. 6, the second pivot shaft 40 is allowed to drive the linking wheel 72 to pivot in a direction opposite to the pivotal direction of the first pivot shaft 30 (the linking wheel 71). Meanwhile, in the pivotal process of the second pivot shaft 40, the periphery of the linking wheel 72 is propped against the movable wheel 73 to cause the movable wheel 73 to embed into the positioning concave portion 712 of the linking wheel 71, enabling the first pivot shaft 30 to turn into an unpivoted lock condition. Then, as shown in FIG. 7, the positioning concave portion 722 of the linking wheel 72 is pivoted to face toward the movable wheel 73 to release the propping contact to the movable wheel 73 until the second pivot shaft 40 drives the linking wheel 72 to pivot with a predetermined angle (about 180 degrees in the figures). Accordingly, it is convenient that, after each use, one of the first and second pivot shafts 30 and 40 can be reversely pivoted in advance to recover to the initial folding condition thereof.
In practice, however, the conventional double rotary shaft hinge device has following difficulties required to be solved. Firstly, because the movable wheel 73 is configured between the linking wheels 71 and 72, sequence rotational control of the first and second pivot shafts 30 and 40 may be functionally failed if the entire volume is reduced. Moreover, because the distance between the first and second pivot shafts 30 and 40 is not easy to be shortened, the product design is affected therewith and small, delicate products cannot be obtained. Secondly, when the first pivot shaft 30 (or the second pivot shaft 40) is pivoted, the second pivot shaft 40 (or the first pivot shaft 30) may be simultaneously tilted to push against the movable wheel 73 together with the first pivot shaft 30, thus to keep the movable wheel 73 to simultaneously contact the first and second pivot shafts 30 and 40. Thus, torque value of the pivoting first pivot shaft 30 (or the second pivot shaft 40) will be directly affected by the frictional force generated from the contact of the movable wheel 73 and the second pivot shaft 40 (or the first pivot shaft 30), and pivotal smoothness of the first and second pivot shafts 30 and 40 is changed accordingly.